7

With circuit switching, you have a 1-to-1 circuit with some predefined channel capacity which is guaranteed. For it to work, you must first establish a circuit/connection before you send any data, and break the connection after. With packet switching, it's somewhat like the local post office - you bring the packets, send them, and let the other devices ...


4

A "circuit" doesn't necessarily mean the same thing as a physical electrical circuit. That's where the term started out, but when various multiplexing schemes were invented, such as TDM, "circuit" acquired the meaning of a certain channel or slot inside the physical connection. In the T-carrier system, for example, the unit called the "circuit" is the 64kbps ...


4

Shared memory and port buffering are not mutually exclusive: Packets payloads will be stored in shared memory prior to being transmitted (think how inefficient it would be to store a broadcast frame 48 different times in order to flood it out each port). Port buffering comes into play when multiple packets arrive at the switch from different ingress ...


4

If the frames entering the switch are using a 1G port, but are being forwarded out a 100M port, then it's likely that frames are coming in faster than they are going out. So they need to be buffered until they can all be transmitted.


3

In circuit switched connection: a connection is always established from end to end before transferring data. in the general case the connection has fixed capacity for the whole duration of the connection even if you don't transmit any useful data and at the same time other connections can;t use your capacity the whole capacity is guaranteed the speed of ...


3

This question has been asked at least a dozen times. We can only guess why the spec says what it says -- no one here wrote it. Despite what the spec says, no one does that -- "ingress filtering" is always enabled on a VLAN aware switch: if vlan 20 isn't not assigned to the port, anything tagged 20 will be dropped. As for untagged traffic, yes, it too (...


3

What is the difference between Switch Fabric Capacity and Forwarding Rate of a switch? Switch Fabric Capacity: It usually means the maximum rate the hardware can move information between cards/ports. However it does not account for time spent looking up output port for frames and packets, for instance. Forwarding Rate: It usually means the maximum rate the ...


2

Remember that what you are looking at is marketing material. The Switch Fabric Capacity is listed in bits per second (bps) and is usually double what it really does since the vendors count full duplex. The Forwarding Rate is measured in packets per second (pps) and is based on an arbitrary packet size which make the vendor look good. You really need to ...


2

In a hub, all the ports are electrically connected, and only one device at a time can talk on the wire. If more then one device talks at the same time, it creates a collision, so hub ports are all half-duplex. In a switch, each port is isolated, and traffic from one port is selectively sent to other ports, so there are no collisions in the switch. Unlike a ...


2

The mode/speed is configured on the switch port! So you could have 12 ports in half-duplex(for devices that don't support full-duplex) and 12 ports in full-duplex. On the assumption that you're on a physical "star topology", those in "half" won't disrupt the others.


2

Configure each VLAN with "no shutdown." Make sure that the VLANs are active. "Conf t" and the type "vlan 2" and see if that brings the VLAN up. Do this with the rest of the VLANs. Make sure that each switch has all VLANs configured, or else you won't be able to trunk those VLANs. This should solve your problem...


2

A broadcast frame is forwarded to all switch ports but the one it was received from. When several switches are connected to each other the broadcast will eventually reach all ports in this broadcast domain. That is unless you've got VLANs set up. VLANs separate the network into distinct broadcast domains that do not communicate with each other on layer 2 (...


2

You don't mention brand of the switch, any management software, or any configuration (in particular how that interface was previously configured), so I can only answer generically. Most default switch MAC address tables have a relatively low timeout to age out entries. Just because you are only seeing 19 devices from the same VLAN on a port currently doesn'...


2

This is a lot more complex than just a software-selectable forwarding option - and is true not only for Cisco but most other vendors. First of all - store-and-forward vs cut-through generally isn't software selectable on most switches. It's potentially available if the speeds of ingress and egress ports are equivalent but as soon as multiple speeds are ...


2

It rather depends on what is real. 24V 6.5W is not 24V 0.5 A - but I think the latter number is just what the default (passive) POE power brick is, and they are oversized somewhat by default. 24V 0.5A would be 12W. 24 of those would be 288W and require the 500W switch. 6.5W X 24 ports would be 156W and the 250W would be fine. Actual data update - not ...


2

I don't know the exact model you are using, but the specs I read say 48V @.5A. That's 24 watts (and is more inline with similar APs) 23 ports @ 24W = 552 Watts. So, no, you can't power all the devices. Also don't forget to account for 50-75 watts for the switch itself.


2

On switch 2, the client ports are on VLAN 100 and 200 (not 10 and 20). EDITED to include Marc Luethi's comment: On ESW2, the switchports where R1, R2, R3 are connected are without spanning-tree portfast. That will leave these switchports in LIS/LRN spanning tree state for at least 30 seconds after they get 'line protocol up'. That might be long ...


2

If you plan to create a ring of switches, all those switches need to support RSTP or MSTP. That is, unless all the unmanaged switches completely ignore IEEE 802.1D and actually forward the RSTP BPDUs - which is very ugly but quite common. (That way, the RSTP switch sees its own BPDUs from one ring port coming in through the other one, and blocks the one with ...


2

EX4300s have four QSFP+ ports (rear panel) which may be used for stacking or as 40GbE. They also don't require an uplink module (EX-UM-xxx) and therefore have four SFP+ 1/10G ports (front panel) in the base model. The newer software on EX4300 makes one shocking choice you need to be aware of. STP may be disabled in a factory-default configuration. That ...


2

If you're looking at purchasing new hardware, EX4300s are generally recommended. It's not that there's anything wrong with the EX4200, it's simply that the EX4300 is the next generation with new features, longer term support, etc. Technically speaking, without getting into all of the finite variations on each model within both platforms, the main ...


2

This seems to assume that queues can have limited number of packets (true enough), but unlimited packet size (not true). The idea that a large message packet size uses fewer places in the queue is true, but it ignores reality that an interface can only serialize the packet bits at a certain speed (bandwidth), so that larger packets take proportionally longer ...


1

On Cisco devices, SVI's are configured just like a physical interface. They are named for the vlan they're attached to. For example, the SVI for Vlan 10 is named interface vlan10. To assign an IPv4 address to it, you would type: interface vlan10 ip address 192.0.2.1 255.255.255.0


1

An SVI is a Switched Virtual Interface. It is an interface for the VLAN itself on the switch. It can be a layer-3 interface (IP addressing) to allow the switch itself to participate in the VLAN. A layer-2 switch can use a layer-3 SVI as its management interface, and it would also need a default gateway in the VLAN to allow the management interface to be ...


1

An access port that receives tagged traffic will drop the tagged frames.


1

Your problem is that the VTP passwords don't match. On the non-working switch: MD5 digest : 0xB9 0x07 0xEE 0xE3 0x27 0xEC 0xF7 0x33 0x98 0x81 0x0A 0xA3 0x32 0xE9 0xD2 0xDF On the working switch: MD5 digest : 0x39 0x28 0x36 0x47 0xDE 0xDC 0xBE 0x26 ...


1

You still need to configure the VLAN 3 SVI on the L3 switch. You also need to set trunk mode and encapsulation on Fa0/24 of all three L2 switches.


1

Specifically concerning negotiate or nonegotiate ... By default, the negotiation port setting is on, that is , the ability to negotiate a trunk port (if not a trunk the port becomes an access port.) To see all a ports settings use the useful command show interfaces switchport NOTE: nonegotiation can be used on an access link as well, a clue why it is used -...


1

A message could be circuit switched or packet switched. You would probably classify message switching as an application layer construct. Packet switching can break a large message into smaller packets to be sent, but a message may be small enough to fit into a single packet, too. A circuit could carry a message over a circuit switched network. It's kind ...


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